Are battery level indicators inaccurate on Android smartphones?

Are battery level indicators accurate or not on Android devices (and all other mobile devices, for that matter)? This question has always been asked, with arguments in favor of both possible answers.

Modaco has published a post in which battery level indicators of the HTC One, in various stages of discharging, are measured and analyzed and, without doubt, there are situations in which the percentage and the battery graph don’t quite match.

Just out of curiosity, I’ve decided to do a somewhat similar measurement on a Sony Xperia T, to see what happens. So I just took a screenshot of the screen, cropped the part showing the battery level and printed it on a sheet of paper.

Then, I measured the whole battery indicator (which was, on my sheet of paper, around 15 milimeters), and then divided it by 10. So, per my calculation, 10% battery level accounted for around 1.5 milimeters on the sheet of paper (see image below if you don’t believe me).

Since the battery was at 72%, I calculated that the battery level indicator should be at 10.8 milimeters; the value I’ve measured on the paper was around 11 milimeters. I admit to not having a tool to measure smaller units around. So, I can say that the indicator was right on the spot (or very close to that).

I tried it again, this time when the battery was at 60%. That would mean 9 milimeters on my sheet of paper, and that’s what it was; it was accurate again. It’s true that, for said device, the percentage is shown next to graphic indicator, so a big difference would be pretty visible (which is why it wouldn’t be too smart for the manufacturer to try anything of the sort).

I do admit to not trying to do any more screen capturing, printing and measuring batteries on pieces of paper, but that convinced me that, at least in these two situations, the Xperia T’s battery level indicator was not trying to deceive me. I can’t vouch for it in any other situations and, after this experiment and after reading the article I was mentioning earlier, I’m not sure what to think anymore.

Of course, these are just a couple of examples. There are a bunch of smartphones out there, all with virtually untested battery indicators. Have you noticed any inaccuracies on your device?